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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package escape
import (
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
"cmd/compile/internal/typecheck"
"cmd/compile/internal/types"
"cmd/internal/src"
)
// call evaluates a call expressions, including builtin calls. ks
// should contain the holes representing where the function callee's
// results flows.
func (e *escape) call(ks []hole, call ir.Node) {
argument := func(k hole, arg ir.Node) {
// TODO(mdempsky): Should be "call argument".
e.expr(k.note(call, "call parameter"), arg)
}
switch call.Op() {
default:
ir.Dump("esc", call)
base.Fatalf("unexpected call op: %v", call.Op())
case ir.OCALLFUNC, ir.OCALLINTER:
call := call.(*ir.CallExpr)
typecheck.AssertFixedCall(call)
// Pick out the function callee, if statically known.
//
// TODO(mdempsky): Change fn from *ir.Name to *ir.Func, but some
// functions (e.g., runtime builtins, method wrappers, generated
// eq/hash functions) don't have it set. Investigate whether
// that's a concern.
var fn *ir.Name
switch call.Op() {
case ir.OCALLFUNC:
v := ir.StaticValue(call.Fun)
fn = ir.StaticCalleeName(v)
}
fntype := call.Fun.Type()
if fn != nil {
fntype = fn.Type()
}
if ks != nil && fn != nil && e.inMutualBatch(fn) {
for i, result := range fn.Type().Results() {
e.expr(ks[i], result.Nname.(*ir.Name))
}
}
var recvArg ir.Node
if call.Op() == ir.OCALLFUNC {
// Evaluate callee function expression.
calleeK := e.discardHole()
if fn == nil { // unknown callee
for _, k := range ks {
if k.dst != &e.blankLoc {
// The results flow somewhere, but we don't statically
// know the callee function. If a closure flows here, we
// need to conservatively assume its results might flow to
// the heap.
calleeK = e.calleeHole().note(call, "callee operand")
break
}
}
}
e.expr(calleeK, call.Fun)
} else {
recvArg = call.Fun.(*ir.SelectorExpr).X
}
// argumentParam handles escape analysis of assigning a call
// argument to its corresponding parameter.
argumentParam := func(param *types.Field, arg ir.Node) {
e.rewriteArgument(arg, call, fn)
argument(e.tagHole(ks, fn, param), arg)
}
args := call.Args
if recvParam := fntype.Recv(); recvParam != nil {
if recvArg == nil {
// Function call using method expression. Receiver argument is
// at the front of the regular arguments list.
recvArg, args = args[0], args[1:]
}
argumentParam(recvParam, recvArg)
}
for i, param := range fntype.Params() {
argumentParam(param, args[i])
}
case ir.OINLCALL:
call := call.(*ir.InlinedCallExpr)
e.stmts(call.Body)
for i, result := range call.ReturnVars {
k := e.discardHole()
if ks != nil {
k = ks[i]
}
e.expr(k, result)
}
case ir.OAPPEND:
call := call.(*ir.CallExpr)
args := call.Args
// Appendee slice may flow directly to the result, if
// it has enough capacity. Alternatively, a new heap
// slice might be allocated, and all slice elements
// might flow to heap.
appendeeK := e.teeHole(ks[0], e.mutatorHole())
if args[0].Type().Elem().HasPointers() {
appendeeK = e.teeHole(appendeeK, e.heapHole().deref(call, "appendee slice"))
}
argument(appendeeK, args[0])
if call.IsDDD {
appendedK := e.discardHole()
if args[1].Type().IsSlice() && args[1].Type().Elem().HasPointers() {
appendedK = e.heapHole().deref(call, "appended slice...")
}
argument(appendedK, args[1])
} else {
for i := 1; i < len(args); i++ {
argument(e.heapHole(), args[i])
}
}
e.discard(call.RType)
case ir.OCOPY:
call := call.(*ir.BinaryExpr)
argument(e.mutatorHole(), call.X)
copiedK := e.discardHole()
if call.Y.Type().IsSlice() && call.Y.Type().Elem().HasPointers() {
copiedK = e.heapHole().deref(call, "copied slice")
}
argument(copiedK, call.Y)
e.discard(call.RType)
case ir.OPANIC:
call := call.(*ir.UnaryExpr)
argument(e.heapHole(), call.X)
case ir.OCOMPLEX:
call := call.(*ir.BinaryExpr)
e.discard(call.X)
e.discard(call.Y)
case ir.ODELETE, ir.OPRINT, ir.OPRINTLN, ir.ORECOVERFP:
call := call.(*ir.CallExpr)
for _, arg := range call.Args {
e.discard(arg)
}
e.discard(call.RType)
case ir.OMIN, ir.OMAX:
call := call.(*ir.CallExpr)
for _, arg := range call.Args {
argument(ks[0], arg)
}
e.discard(call.RType)
case ir.OLEN, ir.OCAP, ir.OREAL, ir.OIMAG, ir.OCLOSE:
call := call.(*ir.UnaryExpr)
e.discard(call.X)
case ir.OCLEAR:
call := call.(*ir.UnaryExpr)
argument(e.mutatorHole(), call.X)
case ir.OUNSAFESTRINGDATA, ir.OUNSAFESLICEDATA:
call := call.(*ir.UnaryExpr)
argument(ks[0], call.X)
case ir.OUNSAFEADD, ir.OUNSAFESLICE, ir.OUNSAFESTRING:
call := call.(*ir.BinaryExpr)
argument(ks[0], call.X)
e.discard(call.Y)
e.discard(call.RType)
}
}
// goDeferStmt analyzes a "go" or "defer" statement.
func (e *escape) goDeferStmt(n *ir.GoDeferStmt) {
k := e.heapHole()
if n.Op() == ir.ODEFER && e.loopDepth == 1 && n.DeferAt == nil {
// Top-level defer arguments don't escape to the heap,
// but they do need to last until they're invoked.
k = e.later(e.discardHole())
// force stack allocation of defer record, unless
// open-coded defers are used (see ssa.go)
n.SetEsc(ir.EscNever)
}
// If the function is already a zero argument/result function call,
// just escape analyze it normally.
//
// Note that the runtime is aware of this optimization for
// "go" statements that start in reflect.makeFuncStub or
// reflect.methodValueCall.
call, ok := n.Call.(*ir.CallExpr)
if !ok || call.Op() != ir.OCALLFUNC {
base.FatalfAt(n.Pos(), "expected function call: %v", n.Call)
}
if sig := call.Fun.Type(); sig.NumParams()+sig.NumResults() != 0 {
base.FatalfAt(n.Pos(), "expected signature without parameters or results: %v", sig)
}
if clo, ok := call.Fun.(*ir.ClosureExpr); ok && n.Op() == ir.OGO {
clo.IsGoWrap = true
}
e.expr(k, call.Fun)
}
// rewriteArgument rewrites the argument arg of the given call expression.
// fn is the static callee function, if known.
func (e *escape) rewriteArgument(arg ir.Node, call *ir.CallExpr, fn *ir.Name) {
if fn == nil || fn.Func == nil {
return
}
pragma := fn.Func.Pragma
if pragma&(ir.UintptrKeepAlive|ir.UintptrEscapes) == 0 {
return
}
// unsafeUintptr rewrites "uintptr(ptr)" arguments to syscall-like
// functions, so that ptr is kept alive and/or escaped as
// appropriate. unsafeUintptr also reports whether it modified arg0.
unsafeUintptr := func(arg ir.Node) {
// If the argument is really a pointer being converted to uintptr,
// arrange for the pointer to be kept alive until the call
// returns, by copying it into a temp and marking that temp still
// alive when we pop the temp stack.
conv, ok := arg.(*ir.ConvExpr)
if !ok || conv.Op() != ir.OCONVNOP {
return // not a conversion
}
if !conv.X.Type().IsUnsafePtr() || !conv.Type().IsUintptr() {
return // not an unsafe.Pointer->uintptr conversion
}
// Create and declare a new pointer-typed temp variable.
//
// TODO(mdempsky): This potentially violates the Go spec's order
// of evaluations, by evaluating arg.X before any other
// operands.
tmp := e.copyExpr(conv.Pos(), conv.X, call.PtrInit())
conv.X = tmp
k := e.mutatorHole()
if pragma&ir.UintptrEscapes != 0 {
k = e.heapHole().note(conv, "//go:uintptrescapes")
}
e.flow(k, e.oldLoc(tmp))
if pragma&ir.UintptrKeepAlive != 0 {
tmp.SetAddrtaken(true) // ensure SSA keeps the tmp variable
call.KeepAlive = append(call.KeepAlive, tmp)
}
}
// For variadic functions, the compiler has already rewritten:
//
// f(a, b, c)
//
// to:
//
// f([]T{a, b, c}...)
//
// So we need to look into slice elements to handle uintptr(ptr)
// arguments to variadic syscall-like functions correctly.
if arg.Op() == ir.OSLICELIT {
list := arg.(*ir.CompLitExpr).List
for _, el := range list {
if el.Op() == ir.OKEY {
el = el.(*ir.KeyExpr).Value
}
unsafeUintptr(el)
}
} else {
unsafeUintptr(arg)
}
}
// copyExpr creates and returns a new temporary variable within fn;
// appends statements to init to declare and initialize it to expr;
// and escape analyzes the data flow.
func (e *escape) copyExpr(pos src.XPos, expr ir.Node, init *ir.Nodes) *ir.Name {
if ir.HasUniquePos(expr) {
pos = expr.Pos()
}
tmp := typecheck.TempAt(pos, e.curfn, expr.Type())
stmts := []ir.Node{
ir.NewDecl(pos, ir.ODCL, tmp),
ir.NewAssignStmt(pos, tmp, expr),
}
typecheck.Stmts(stmts)
init.Append(stmts...)
e.newLoc(tmp, true)
e.stmts(stmts)
return tmp
}
// tagHole returns a hole for evaluating an argument passed to param.
// ks should contain the holes representing where the function
// callee's results flows. fn is the statically-known callee function,
// if any.
func (e *escape) tagHole(ks []hole, fn *ir.Name, param *types.Field) hole {
// If this is a dynamic call, we can't rely on param.Note.
if fn == nil {
return e.heapHole()
}
if e.inMutualBatch(fn) {
if param.Nname == nil {
return e.discardHole()
}
return e.addr(param.Nname.(*ir.Name))
}
// Call to previously tagged function.
var tagKs []hole
esc := parseLeaks(param.Note)
if x := esc.Heap(); x >= 0 {
tagKs = append(tagKs, e.heapHole().shift(x))
}
if x := esc.Mutator(); x >= 0 {
tagKs = append(tagKs, e.mutatorHole().shift(x))
}
if x := esc.Callee(); x >= 0 {
tagKs = append(tagKs, e.calleeHole().shift(x))
}
if ks != nil {
for i := 0; i < numEscResults; i++ {
if x := esc.Result(i); x >= 0 {
tagKs = append(tagKs, ks[i].shift(x))
}
}
}
return e.teeHole(tagKs...)
}
|